Recent wireless communication appliances, including portable telephones and wireless LAN devices, are designed and manufactured in progressively smaller and thinner packages. Such wireless communication appliances are assembled from numerous components including various SAW devices suitable for performing filtering and resonating functions. It is preferable, perhaps even necessary, for these devices to present a form factor having a smaller footprint and/or occupies a smaller volume. Therefore these devices must be packaged with minimal dimensions. In certain applications hermetic packages may also be required.
Conventional SAW filters may be manufactured according to the following process: a circuit for a SAW filter, typically formed on a piezoelectric substrate, is mounted on an LTCC (low temperature co-fired ceramic) substrate via a flip-chip or a wire bonding connection process. The exterior of the piezoelectric substrate, with the exception of the bottom surface in contact with the LTCC substrate, is then covered with a layer of polymer material. The outer surface of the polymer is coated with a metal layer to provide shielding (both electromagnetic and physical shielding) and to protect the active region of the SAW filter, the input/output bonding pads, and terminals (typically solder bumps that are positioned on the bottom surface of the SAW filter substrate) from external environmental factors. The LTCC substrate with the SAW filter attached is then mounted and electrically connected to a printed circuit board (e.g., a motherboard). The LTCC substrate and other associated components, are encapsulated with an encapsulate material.
The above-described manufacturing process is lengthy and expensive, as the piezoelectric substrate is essentially mounted twice, first on the LTCC substrate and then the LTCC substrate is mounted on the printed circuit board. Also, this two step mounting process increases the size of the mounted SAW filter because the size of the LTCC substrate on which the SAW filter is mounted is larger than that of the SAW filter piezoelectric substrate.